Unified Non-Inverting and Inverting PWM AC-AC Converter With Versatile Modes of Operation

This paper proposes unified non-inverting and inverting AC-AC converter (UNI-AC) using pulse width modulation (PWM) for the utility voltage compensation. It offers four effective switching states to regulate the output voltage in bipolar manner, facilitating versatile modes of operation with different number of switching states being modulated. Each mode of the proposed UNI-AC is able to compensate both the grid voltage sag and swell problems due to its bipolar voltage gain. The operational principle and comparison for all these modes are investigated in details. Also, the UNI-AC is reversible and compatible with full range of power factor. Other technical merits offered by the proposed approach include the compact hardware installation, reduced switch voltage stress (also low dv/dt) and decreased control complexity. Detailed analysis and experimental verification are presented in this paper

An improved bipolar-type AC-AC converter topology based on non-differential dual-buck PWM AC choppers

A novel single-phase pulse width modulation (PWM) direct ac-ac converter based on two-level non-differential dual-buck ac chopper legs with inverting and non-inverting operations is first proposed in this paper. It has the ability to resolve both voltage sag and swell problems at the same time when used as distributed flexible voltage conditioner (DFVC).Compared to the traditional ac-ac converter, it has much enhanced system reliability thanks to no shoot-through problems even when all switches of each ac chopper legs are turned on, and therefore, the PWM dead-time is not needed leading to improving the utilization of the duty cycles. Only half of the switches in the proposed converter are switched at high frequency during a switching period at most, which significantly reduces the total switching loss. In particularly, the converter has two greatest advantages that it retains the common sharing ground of the input and output and has the same buck/boost operation process for non-inverting and inverting modes. In order to fully testify the performance of the proposed converter, a 500W experimental prototype is built and tested at different conditions